A recording tape cartridge as shown in FIGS. 2 and 3 which is so called a small size video tape cartridge is provided with a lid member 2 in the front portion of a case body 1 for opening and closing the front face of the case body to cover a recording tape 3.
In the conventional cartridge of the above type, the supporting mechanism of the lid member 2 is arranged in such a manner that there are formed a pair of supporting holes 4 on the front end portion of the left side wall and the right side wall 6 of the case body 1 and a pair of supporting shafts 5 is formed on the inside faces of side arms 2b of the lid member 2, whereby the lid member 2 is mounted on the front portion of the case body 1 by fitting the side arms 2b to the outside of the case body deforming the side arms 2b resiliently outwardly, then recovering the deformation of the side arms 2b, thus, the supporting shafts 5 are inserted in the corresponding supporting holes 4, so that the lid member 2 can be rotatably mounted on the front portion of the case body 1. The lid member 2 can be rotatably held on the case body 1 by defining the length of the supporting shafts 5 and the depth of the supporting holes 4 to be sufficiently large.
However, according to the conventional lid mounting as described above, in making the size of the cartridge smaller, there may occur a problem as mentioned hereinafter. In making the size of the tape cartridge small, the thickness of both side walls 6 of the case body 1 is necessarily decreased, thereby resulting in decreasing the depth of the supporting holes 4. On the other hand, if the length of the supporting shafts 5 is large, the supporting shafts 5 may be unduly projected inside of the case body 1 through the side walls 6, thus, the free end portion of the projection 5 abuts onto the recording tape which results in preventing smooth running of the recording tape. To avoid this, the supporting shafts must be short as the size of the cartridge is small. Under such arrangement, even if the lid member is once assembled correctly on the case body, the supporting shafts 5 would be easily disengaged from the supporting holes 4 by an impact or vibration applied to the case body 1. In order to avoid such disengagement of the supporting shafts from the holes, flanges 5a are provided on the free end portions of the supporting shafts, with the diameter of the flange 5a larger than the diameter of the supporting shafts. In this arrangement, however, since the supporting shafts 5 can not be inserted in the hole 4, a recess a is formed on the top section 1a and another recess b on the the bottom section 1b to form an opening similar to the hole 4 for insertion of the projection 5 when both sections 1a and 1b are assembled together as shown in FIGS. 1(I), (II) and (III). In this arrangement, the lid member 2 is assembled on the top section 1a by merely putting the supporting shafts 5 preliminarily on the recesses a without specific holding, therefore, the lid member 2 is easily disengaged from the top section 1a. Even if a spring 21 for exerting the lid member 2 toward the closed position is attached between the lid member and the top section, although the lid member 2 can be preliminarily held on the top section, there still remains a possibility of disengagement of the lid member 2 from the top section 1a. If the lid member is easily disengageable from the top section, there may occur a failure in assembling of the recording tape cartridge in the process of manufacturing of the cartridge, thereby preventing an automatic production of the recording tape cartridge.